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Analog Devices Inc. LTC3859AIUHF#TRPBF
- Part No.:
- LTC3859AIUHF#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-WFQFN Exposed Pad
- Datasheet:
-
LTC3859AIUHF#TRPBF.pdf
- Description:
- IC REG CTRLR MULT TOPOLOGY 38QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,298
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Product details
Overview
LTC3859AIUHF#TRPBF from Analog Devices is a triple-output synchronous DC/DC controller (buck/buck/boost) driving all-N-channel MOSFET stages, featuring 55μA no-load quiescent current, 0.8V/1.2V precision references for buck and boost outputs respectively, and phase-lockable switching frequency up to 850kHz - deployed in automotive start-stop systems requiring cold-crank operation down to 2.5V input.
For engineers reviewing the LTC3859AIUHF#TRPBF datasheet, LTC3859AIUHF#TRPBF pinout, LTC3859AIUHF#TRPBF application, or LTC3859AIUHF#TRPBF equivalent, key selection criteria include its triple-output topology with independent RUN control, OPTI-LOOP compensation for wide output capacitor/ESR tolerance, and Burst Mode® optimization for high-input-voltage boost regulation.
Technical Context
The LTC3859AIUHF#TRPBF integrates three independent current-mode controllers: two buck channels with 99% dropout duty cycle and one boost channel supporting 100% synchronous MOSFET duty cycle even in Burst Mode®; each uses dedicated ITH error amplifier outputs and differential SENSE+/- inputs for RSENSE or DCR current sensing.
Its PLLIN/MODE pin selects among Burst Mode®, pulse-skipping, or forced continuous conduction mode across all channels simultaneously, while FREQ pin enables resistor-programmable switching frequency (50–900kHz) or external synchronization (75–850kHz), and VBIAS supports wide 4.5V–38V input with auxiliary bias down to 2.5V post-startup.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Topology | Buck/Buck/Boost triple-output synchronous controller - enables single-chip multi-rail power for mixed-voltage SoC or sensor subsystems. |
| Quiescent Current | 55μA (one channel active) - extends battery runtime in always-on automotive or portable applications. |
| Reference Voltage | 0.8V ±1.2% for bucks; 1.2V ±1.2% for boost - ensures tight output regulation across temperature and load. |
| Switching Frequency | Programmable 50–900kHz or syncable 75–850kHz - balances efficiency, size, and EMI in space-constrained designs. |
| Input Voltage Range | 4.5V–38V main bias; operates down to 2.5V when biased from boost output - supports cold-crank and wide automotive supply range. |
| Output Voltage Range | Buck: 0.8V–24V; Boost: up to 60V - accommodates diverse rail requirements including USB PD, industrial sensors, and LED drivers. |
| Gate Drive Strength | TG3/BG3: 1.2Ω pull-up / 1.0Ω pull-down - drives high-side/lower-side N-MOSFETs efficiently at high switching frequencies. |
Pinout & Package
Package: 38-pin 5mm × 7mm plastic QFN (UHF) with exposed PGND pad (Pin 39) requiring PCB soldering for thermal and electrical performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| RUN1, RUN2, RUN3 | Digital enable inputs per channel | Independent shutdown control: <1.17V (buck) or <1.20V (boost) disables respective regulator; all <0.7V enters 14μA shutdown. |
| VFB1, VFB2, VFB3 | Feedback voltage inputs | Monitor output via resistive divider; regulate to 0.8V (buck) or 1.2V (boost); PGOOD1 monitors only VFB1. |
| TG1/TG2/TG3, BG1/BG2/BG3 | Top/bottom gate drivers | Drive N-MOSFET gates; TG swing = INTVCC + SW node voltage; BG swing = GND to INTVCC. |
| SENSE1+/−, SENSE2+/−, SENSE3+/− | Differential current sense inputs | Support RSENSE or DCR sensing; SENSE3+ supplies current to comparator; SENSE1,2− sources current when >INTVCC. |
| PLLIN/MODE | Mode selection & sync input | GND = Burst Mode®; INTVCC = forced CCM; 1.2V–(INTVCC−1.3V) = pulse-skipping; external clock = sync mode. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP compensation | Enables stable loop response across wide range of output capacitance (e.g., ceramic + bulk) and ESR without redesign. |
| 100% duty cycle boost operation | Maintains regulation during input voltage drop below output - critical for automotive boost rails during cold crank. |
| Triple independent RUN control | Allows dynamic power sequencing and partial system sleep - e.g., keep boost active for always-on MCU while disabling bucks. |
| Low IQ sleep mode | 55μA with one channel active - meets stringent ISO 16750-2 quiescent current requirements for automotive modules. |
| EXTVCC switchover | Automatically switches INTVCC supply from VBIAS to external 4.7–14V source - improves efficiency and reduces heat in high-VIN systems. |
Applications
| Automotive Start-Stop Systems | Battery-Powered Digital Devices |
|---|---|
Use Scenario: Power management in engine control units (ECUs) that must remain operational during cranking events where battery voltage dips to 2.5V. IC Role / Device Role / Timing Role: Triple-output controller generating 5V (microcontroller), 8.5V (sensor interface), and regulated 10V boost rail (CAN transceiver) from 12V battery. Use Value: Cold-crank capability down to 2.5V input and 55μA sleep current ensure compliance with ISO 16750-2 Class D requirements. |
Use Scenario: Portable medical monitor with isolated analog front-end, low-power MCU, and display backlight requiring multiple regulated rails. IC Role / Device Role / Timing Role: Generates 3.3V buck (MCU), 5V buck (USB interface), and 24V boost (OLED backlight) from single Li-ion cell (3.0–4.2V). Use Value: Ultra-low 55μA quiescent current extends battery life between charges; programmable frequency avoids audible noise in sensitive analog sections. |
| Distributed DC Power Systems | Multioutput Buck-Boost Applications |
Use Scenario: Industrial IoT gateway with Ethernet PHY, RF module, and microcontroller - each requiring different voltage rails and sequencing. IC Role / Device Role / Timing Role: Provides 1.2V (core), 3.3V (I/O), and 5V (PHY) from 24V PoE-derived input using buck/buck/boost architecture. Use Value: Independent RUN pins enable precise power-up/down sequencing; OPTI-LOOP ensures stability with mixed ceramic/tantalum output caps. |
Use Scenario: Automotive infotainment head unit needing 5V (processor), 12V (audio amplifier), and variable 8–16V (LCD bias) from unstable 9–16V vehicle bus. IC Role / Device Role / Timing Role: Dual buck channels deliver fixed 5V/12V; boost channel provides adjustable output tracking VIN above threshold - enabling seamless transition between buck and boost modes. Use Value: 100% duty cycle boost and 99% buck dropout eliminate need for separate LDOs or charge pumps in wide-input-range designs. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar triple-output synchronous controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3859AEUHF#TRPBF | Same pinout and functionality; rated for –40°C to 125°C junction temperature (vs. LTC3859AIUHF#TRPBF's same range but A-grade screening). | No functional difference; used in commercial/industrial environments where extended temperature validation not required. | Select LTC3859AIUHF#TRPBF for automotive AEC-Q100-compliant designs requiring tighter parametric screening over temperature. |
| LTC3859AHUHF#TRPBF | Same architecture; rated for –40°C to 150°C junction temperature with enhanced high-temp reliability testing. | Suitable for under-hood automotive applications (e.g., transmission control) where ambient exceeds 125°C. | Choose LTC3859AHUHF#TRPBF when operating junction temperature may exceed 125°C; otherwise LTC3859AIUHF#TRPBF offers optimal cost/performance balance. |
Compared with LTC3859AEUHF#TRPBF and LTC3859AHUHF#TRPBF, the LTC3859AIUHF#TRPBF delivers identical triple-output buck/buck/boost control and low-IQ performance but is specifically screened to meet automotive-grade reliability standards at –40°C to 125°C, making it the preferred choice for body electronics and ADAS domain controllers.
Availability
LTC3859AIUHF#TRPBF is available at Aetrix Electronics and suitable for automotive start-stop systems, battery-powered digital devices, and distributed DC power systems requiring stable component supply with guaranteed long-term availability and traceable sourcing.
Supply support for LTC3859AIUHF#TRPBF includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Analog Devices, Inc. is a global semiconductor leader specializing in high-performance analog, mixed-signal, and digital signal processing technologies for precision instrumentation, industrial automation, and automotive electronics.
The LTC3859A product line delivers high-efficiency, multi-output synchronous DC/DC controllers optimized for automotive, industrial, and battery-powered applications demanding ultra-low quiescent current and robust cold-crank operation.
FAQ
What is the minimum input voltage required for LTC3859AIUHF#TRPBF startup?
The LTC3859AIUHF#TRPBF requires a minimum 5V on VBIAS to initiate startup; however, once running, it can sustain operation with input as low as 2.5V when biased from the boost output or an auxiliary supply - a key feature for automotive cold-crank resilience. This behavior is confirmed in the Absolute Maximum Ratings and Typical Application sections of the official datasheet.
Does LTC3859AIUHF#TRPBF support independent voltage tracking across its three outputs?
Yes - the LTC3859AIUHF#TRPBF supports independent tracking: TRACK/SS1 and TRACK/SS2 pins allow buck outputs to follow an external voltage ramp during startup, while SS3 controls boost soft-start separately. Each uses internal 1µA current sources, enabling coordinated power-up sequences without external circuitry.
How does the Burst Mode® operation differ between LTC3859A and earlier LTC3859 in boost configuration?
The LTC3859AIUHF#TRPBF improves Burst Mode® regulation accuracy when input voltage exceeds the boost output setpoint - reducing output voltage ripple and improving light-load efficiency compared to the original LTC3859. This enhancement is explicitly documented in the device description and feature list of the Rev. B datasheet.
Can LTC3859AIUHF#TRPBF drive high-side N-MOSFETs without external bootstrap diodes?
No - the LTC3859AIUHF#TRPBF requires external Schottky diodes between BOOSTx and INTVCC pins to charge the bootstrap capacitors for TG1/TG2/TG3 high-side gate drive. The datasheet specifies this in the PIN FUNCTIONS section and typical application schematics, confirming mandatory external diode placement.
What is the maximum achievable boost output voltage using LTC3859AIUHF#TRPBF?
The LTC3859AIUHF#TRPBF supports boost output voltages up to 60V, as specified in the FEATURES table and validated by absolute maximum ratings for BOOST3 (–0.3V to 76V) and SW3 (–5V to 70V). This enables use in industrial sensors, LED drivers, and telecom bias supplies.
LTC3859AIUHF#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 38-WFQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Down, Step-Up/Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck, Buck-Boost, SEPIC
- Number of Outputs:
- 3
- Output Phases:
- 2
- Voltage - Supply (Vcc/Vdd):
- 4.5V ~ 38V
- Frequency - Switching:
- 115kHz ~ 835kHz, 350kHz ~ 535kHz
- Duty Cycle (Max):
- 99%, 100%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Enable, Frequency Control, Power Good, Soft Start, Tracking
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 38-QFN (5x7)
LTC3859AIUHF#TRPBF FAQ
1.How can I place an order for LTC3859AIUHF#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3859AIUHF#TRPBF on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for LTC3859AIUHF#TRPBF reliable?
The price and inventory of LTC3859AIUHF#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3859AIUHF#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3859AIUHF#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3859AIUHF#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3859AIUHF#TRPBF?
LTC3859AIUHF#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3859AIUHF#TRPBF order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for LTC3859AIUHF#TRPBF?
For technical support, including LTC3859AIUHF#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3859AIUHF#TRPBF requirements.
6.How does Aetrix verify that LTC3859AIUHF#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3859AIUHF#TRPBF products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LTC3859AIUHF#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3859AIUHF#TRPBF?
All LTC3859AIUHF#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3859AIUHF#TRPBF, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The LTC3859AIUHF#TRPBF part is unused and in its original packaging.
Return procedure for LTC3859AIUHF#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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